Image transfer device



y 1954 E. R. SABEL ETI'AL 2,684,901

IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 1 Fig. 4 asINVENTORS {pa/00p R- 6/9551- By CL)D R. H

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. IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 2 HIGHvourAc:

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IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 3 INVENTORSPatented July 27, 1954 IMAGE TRANSFER DEVICE Edward R. Sabel and C] N.Y., assignors to The yde R. Mayo, Rochester, Haloid Company, Rochester,N. Y., a corporation of New York Application December 19, 1950, SerialNo. 201,534

6 Claims. 1

This invention relates to image transferring devices and particularly todevices for transferring image material electrostatically from onesurface to another.

An important application of the devices herein disclosed is in theelectrostatic transfer of powder images from electrophotographic platesand from other electrostatic image plates.

In the process of electrophotography, as described, for example, inPatent No. 2,297,891 issued to Chester F. Carlson, anelectrophotographic plate comprising a layer of photoconductiveinsulating material on a conductive base is given an electrostaticcharge, exposed to a light image to create an electrostatic latent imageon its surface, and then dusted with an electroscopic powder to producea powder image. "The apparatus of the present invention is useful intransferring such powder images to sheets of paper. paper offset mats,plastic sheets, and the like.

The devices of the present invention may also be used to transfer powderimages formed on powder printing plate consisting of insulating imagesbonded to metal backings. With such plates powder images can be formedby simply charging the plate frfctionally or with an ion source to laydown an electrostatic charge on the insulating portions. Upon dustingwith powder a powder image is deposited which can be transferred topaper or other sheets by the devices disclosed.

The devices herein disclosed are also useful in transferring other imagematerials which can be transferred electrostatically.

The devices of the present invention include mechanism for advancing animage plate under an ion source and means to feed a transfer sheet tothe plate surface coincident with or prior to passage under the ionsource. The invention also contemplates means for obtain ng registry theimage on the transfer sheet. means for starting and stopping the plateadvance and other features of control. Also contemplated are means toavoid bulges or blisters between the transfer sheet and the plate asthey pass under the ion source.

The invention comprises the features of construction, combination ofelements, arrangement of parts, and methods of operation referred toabove or which will be brought out and exemplifled in the disclosurehereinafter set forth, including the illustrations in the drawing.

In the drawings:

Figure 1 is a top plan view of a transfer device embodying features ofthe present invention;

Figure 2 is a side elevation thereof;

Figure 3 is a vertical section on the line 33 of Figure 1;

Figure 4 is a vertical section on the line 4-4 of Figure 2;

Figure 5 is an enlarged detail view of the transfer sheet feed mechanismtaken from the line 55 of Figure 2;

Figure 6 is a circuit diagram of the electrical controls for the device;

Figure 7 is a side elevation of a modified transfer sheet feed member;and

Figure 3 is a side elevation, partly in section, of a modified transferdevice.

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the constructionand arrangement of parts in the method of operation without departingfrom the spirit of the invention. In the following description and inthe claims parts will be identified by specific names for convenience,but they are intended to be as generic in their application to similarparts a the art will permit.

Referring to the drawings, the transfer device illustrated in Figures 1to 5 inclusive for transferring powder images to individual sheetscomprises a box-like base I 8 upon which is supported a feed chutemechanism H for transfer sheets, such as paper. The chute mechani m I iis supported by a pair of sheet metal standards i2 secured to the topsurface of base ill. An ion source i3 comprising a grid of corona dischrge wires is bridged across the top surface of base l9 substantiallymidway between the ends of base Ill and is supported by a bridge-likerame'l i comprising a crosspiece and two v tical uprights supported nearthe edges of the top of base 5. The grid i3 is strung between insulatingblocks BI and is shielded above by spaced sheet metal shield 62. Asafety shield optionally protects against insertion of foreign obfectsinto the grid.

A pair of endless chains l5 and itpass over sprocket wheels ll which aremounted inside base in and extend through slots in its top surface. Thechains slide over the top surface of base Ill optionally along a metalstrip (not shown) to protect against wear, passing from one end to theother underneath sheet feed mechanism H and corona grid l3. Chain l5passes under a drive sprocket is which is driven by an electric motor l8through speed-reduction gearing.

A stop lever 2!] is also mounted inside the base it and provided withstop projections which extend up through the top of the base underneaththe corona grid 13 to serve as positioning stops for an image plate anda sheet of transfer material. A solenoid H is provided for retractingthe stop arm.

The circuit for energizing the corona grid i3, for starting and stoppingelectric motor 58, and for operating solenoid 2! to retract the stop armis shown in Figure 6. The features of the con trol circuit, as well asspecific details of the device, will be brought out more fully in thefollowing description of the preferred mode of operation.

In operation, an image plate which may comprise a flexible plate or arigid fiat metal plate carrying a powder image on its upper surface islaid on chains [5 and I6 where they rest on the top surface of base itand are underneath the transfer sheet feed mechanism l l. The plate isplaced on the chains and slid forward manually to a position where thetwo corners of its leading edge are against stop pins 22 on step lever23. The plate thus forms a bridge supported along its two edges onchains l5 and i6 and having its leading edge abutted against stop pins22, and sides 12 provide lateral positioning or centering.

A transfer sheet, such as a sheet of paper, or a paper oifset master orother sheet transfer material, is placed on sheet feed mechanism H. Thimechanism comprises means for supporting the edges of the transfer sheetconsisting of a pair of L-shaped sheet metal channels 23' pivoted byhinges 24 to a pair of L-shaped sheet metal side members 25 as seen mostclearly in Figures 3 and 5. Hinges 24 include coil springs (not shown)normally holding channels 23 in the position shown, with the upper edgesof channels 23 abutting the inside faces of the flanges on members 25.

Transfer sheet feed mechanism Ii is provided with means to spread apartguide channels 23 to widen the gap between them and allow the body ofthe transfer sheet to fall against the surface of the image plate. Thismechanism comprises a manually-operable lever 40 secured to a pivotshaft 61 carrying cam pins 42 which slide against cam surfaces 43 ofchannels 23 to swing them outwardly on their hinges 24. Cam surfaces 33are formed by curving the hinge-attached faces of channels 23 outwardlyat their upper ends adjacent cam pins 42 as seen most clearly in Figure5. A pair of stops 44 is provided on the outer face of one of saidmembers 25 to limit the travel or manual lever 40.

The side members 25 are secured to sheet metal uprights l2 so as toslant downwardly from the left-hand end of the device as seen in Figure2 toward the position of the leading edge of an image plate when it ispositioned against stop ins 22. Thus guide channels 23, which aresupported by side members 25, form a paper chute sloping toward theleading edge of the image plate at a substantial angle. In practice anangle of 30 has been found to be suitable although in this embodiment ofthe invention the angle of the chute is not particularly critical andmay be varied some without substantially changing the functioning of thedevice and will be varied to some extent depending on the nature of thetransfer sheet.

The transfer sheet is selected of such width as to have its long edgesresting on the sloping surfaces of guide channels 23 when positioned onthe sheet feed mechanism. The sheet may then be advanced manually downthe chute until its leading edge engages stop plate 26 also supported onstop arm 2% In the embodiment illustrated it is desired to index thetransfer sheet with respect to the image plate so that the leading edgeof the transfer sheet extends a short distance ahead of the leading edgeof the image plate. However, it will be appreciated that, if desired,the image plate and transfer sheet can have their leading edges broughtinto register in which case stop pins 22 may be eliminated and stopplate 26 may serve as the indexing member for both the plate and thetransfer sheet. Having advanced the transfer sheet into abutment withstop plate 26, the operator is now ready to start the transferoperation. At this time the transfer sheet is still suspended above theimage plate and is in contact with it only along a narrow margin at theleading edge of the plate. This creates a curve or channel extendingacross the transfer sheet which tends to straighten out any bulges orkinks in the sheet material and causes the leading edge of the sheet tolie flat against the surface of the plate. In order to obtain a goodelectrostatic transfer of a powder image it is essential that there beintimate contact between the sheet material and the image-carryingsurface throughout the area that passes under the ion source.

The operator now throws switch 21 to On position, if this has notalready been done, and then momentarily presses start switch 36. Thiscloses an energizing circuit (Figure 6) from the power source, such as a-volt A. C. line, through normally closed stop switch 29, start switch28, lock-up relay winding 35] and Off-On switch 2'! to operate relay 3%]and close its holding contacts iii in parallel with switch 28 so thatthe circuit will remain closed when the operator manually releases startswitch 28. A circuit is also completed through contacts 28 or St to ahigh voltage power supply unit 32 for energizing corona grid 53. Powersupply 32 may comprise a step-up transformer and vacuum tube rectifiercircuit of well-known design adapted to deliver a high potential, suchas 6000-8000 volts D. C. to corona grid it, the opposite output terminalbeing connected to machine ground which includes chains 45 and it sothat the image plate will be grounded when it is restin on the chains. Apilot light 33 bridged across the energizing circuit for the highvoltage power supply is also turned on at this time to indicate to theoperator that the corona grid is energized.

A circuit is also completed from contacts 28 or 35 through rectifier3-1, rheostat 35, the parallel arrangement of high resistance relaywinding 36 and condenser 3'1, and switch 27. Rheostat 35 has been presetto a resistance which adjusts the charging rate of condenser 37 to avalue which introduces a predetermined time delay in the operation ofrelay 35 and the relay is marginally operating, requiring a certainminimum of current before it operates. This permits the high voltagepower supply to warm up and grid 13 to become fully energized beforeoperation of relay 36 which controls the drive motor i9 and solenoid 2|.The time delay additionally assures that the leading edge of thetransfer sheet is adequately tacked down onto the image plate before theforward motion begins. When relay 36 operates it closes an energizingcircuit from contacts 3| through the contacts of relay 3%, the windingof solenoid 2i and switch 2'3 to energize the solenoid. Relay 35 alsocloses the operating circuit to one terminal of motor 19 but the motordoes not begin operation at this instant since its circuit is stillincomplete.

Solenoid 2 i, in operating, pulls down its plunger against thecompression of spring 38 and pulls down stop lever by link 39 connectingthe solenoid plunger to the lever. This retracts stop pins 22 and stopplate 26 below the path of travel of the image plate. Operation ofsolenoid 2! also closes microswitch 45: which is controlled by lever 20,thus completin the return circuit from motor l8 through switch '2'! topower source and energizing motor iii to start the advance of the imageplate and transfer sheet by chains :5 and I6.

In operation of the devi e the lever may be operated prior to startswitch to drop the transfer sheet onto the image before the corona gridis energized, but in the preferred mode of operation the operator firstpresses the start switch 28 to energize the power supply which almostimmediately places a charge on the leading edge or margin of thetransfer sheet where it rests against the image plate thereby creatingelectrostatic adhesion of the tra fer sheet margin to the plate, Theoperator turns the lever so to drop the main body of L11 transfer sheetagainst the plate. This is preferred since it avoids the possibilitythat the transfer sheet may shift in position as it falls and therebyget out of register. The electrostatic adhesion prevent this.

As the image plate and transfer sheet pass under the corona grid iii anelectric charge is sprayed onto the of transfer sheet progressivelythroughout its length to produce adhesion between the transfer sheet theunderlying powder image. When the plate advances to end of the chain itsleading edge projecting lever G5 comprising the operating arm of stopswitch 29 which may be snap acting microswitch which is normally closedd which is opened by pressure on the actuati lever. Thus, when the plateengages lever step switch 29 is opened to deenergize power supply 32,release solenoid 2 i, stop motor l9, release relays 30 and 36, therebyunlocking the circuit and preparing it for subsequent manual initiation.The transfer sheet is now removed from the image plate, carrying with itthe transferred powder image. The po vder can be fused onto the sheet inan oven or other fusing device. The image plate with any residual powderimage it may carry, is now removed for cleaning and reuse. As soon asthe plate is removed stop switch 29 closes its contacts but noenergizing circuit is completed until start switch is again operated.

Figure '7 illustrates a modified sheet feed chute 46 comprising a broadand shallow metal channel 4! supported by sheet metal standards 48. Thisfeed chute may be used in place of mechanism ll previously describedwhere flexible transfer sheet materials are used. Since the sheet issupported by a solid metal channel it is not released to fall againstthe image plate in this case but is simply allowed to slide oif thesloping surface of channel t? when it is pulled along by the image platedue to the electrostatic adhesion produced by the corona discharge ontothe leading edge of the transfer sheet.

Figure 8 illustrates a modified transfer device which includes a rollermechanism to between the sheet feed mechanism Ii and the corona grid l3.This mechanism comprises a pair of spaced parallel :netal levers 5ipivoted at one end at 52 and provided with aligned vertical notches 53at their free ends. A rol er 54 which may preferably be formed of softrubber but may be made of other materials such as metal, wood, plasticor the like, has an axial shaft 55 the ends of which are received innotches 53 so that the roller 56 is effectively positioned and guided bylevers 5|. A pair of sheet metal standards 56 is mounted at the edges ofbase it beyond D the ends of shaft 55 and a shaft 5? is pivoted inaligned openings near the top of the standards and provided with manuallever at one end. An L-shaped link 53 is provided at each end of theroller, each of the links being pivoted at one end in the body of alever 5i and at the other end to a crank lever to on shaft 5?. Bymanually rotating shaft 5? through an angle of approximately 90 levers5i are lifted by links 53 to lift roller 54 to a position clearing thepath of travel of the image plate. This renders the roller inoperative.

In operation, plate 83 is placed on the conveyor and manually advancedagainst stops and a transfer sheet 64 is advanced down t e chute of feedmechanism H underneath roller '5; until its leading edge is underneathcorona grid i3 and in contact with stop 26. Manual rotation of shaft 51in a counterclockwise direction as seen in Figure 8 will then lowerroller 5d against the top face of the transfer sheet. Then, as the imageplate is advanced under the corona grid i3, roller 5 serves to smoothdown the shee before it under the corona grid. This roller is ofparticular advantage in the case of sheet materials which tend to beslightly irregular or which contain bulges or creases.

It has been seen that transfer mechanisms have been provided accordingto the present invention for transferring powder imageselectrostatically from rigid or flexible surfaces to individual sheetsof paper, plastic and the like and to offset While the presentinvention, as to its objects and advantages, has been described nereinas carried out in specific embodiments thereof, is not desired to belimited thereby but it is intended to cover the invention broadly withinthe spirit and scope of the appended claims.

What is claimed is:

l. A transfer device for l -aterial from an image sheet, comp ing incombination,

an image plate, a transfer sta' to advance a plate on said supportparallel to the plate so "ace pas said transfer ireeted toan acuterespect to station, a sheet feed uide r .nio trans T18 on CL or c age 0sheet may be electrostatically image plate while the major part of t1 2is still at said acute angle to sa d ioage plate and a curved channel isfor d for sheet to thereby eli "late bulges in the portion of the sheetclamped again t the image plate, means to retract s t feed guide meansto drop the trailing tion of the transfer sheet onto image plate.

2. A transfer device for transferring an image material from an imageplate to a transfer sheet, comprising in combination, a support for animage plate, a transfer station, drive means to advance a plate on saidsupport in a path transparallel to the plate surface past said transferstation, a sheet feed guide directed toward said path of plate advanceat an acute angle greater than 30 degrees with respect to the surface ofsaid plate to feed a transfer sheet to the surface of a platepositioned. on said support at said acute angle and to a position insaid path adjacent said transfer station, stop means to position theleading edges of said plate and transfer sheet prior to passing saidtransfer station, and means to retract said stop means and to energizesaid plate advance and discharge source, and an electric dischargesource at said transfer station above said path of plate travel forproducing an electric discharge onto the back of a transfer sheetoverlying an image plate on said support, whereby the leading edge of atransfer sheet may be electrostatically clamped to an image plate whilethe major part of the sheet is still at said acute angle to said imageplate and a curved channel is formed across the transfer sheet tothereby eliminate bulges in the portion of the sheet clamped against theimage plate.

3. A transfer device for the electrostatic transfer of imagescomprising, in combination, an elec tric ion source, an electricallydriven plate advance motor operatively connected to drive means to passan image plate and superimposed transfer sheet under said source, aswitch for initiating the energization of said ion source and said plateadvance motor, a lock-up relay for maintaining said source and saidadvance motor energized, and a disconnect switch for deenergizing saidlock-up relay to stop said motor and deenergize said ion sourceresponsive to the completion of travel of an image plate under andbeyond said source.

4. A transfer device for the electrostatic transfer of imagescomprising, in combination, .a corona discharge electrode and anenergizing circuit therefor, an electrically driven plate advance motoroperatively connected to drive means to pass an image plate andsuperimposed transfer sheet under said source, a manual switch forinitiating the energization of said corona cir cuit and said plateadvance motor, a lock-up relay for maintaining said corona circuit andsaid advance motor energized, and a disconnect switch for deenergizingsaid lock-up relay to stop said motor and deenergize said corona circuitresponsive to the completion of travel of an image plate under andbeyond said electrode.

5. A transfer device for the electrostatic transfer of imagescomprising, in combination, a corona discharge electrode, a motor drivenplate advance mechanism to pass an image plate and superimposed transfersheet under said electrode, a stop for indexing said image plate andtransfer sheet with respect to each other prior to passage thereof undersaid electrode, an electromagnet for retracting said stop from its operative position, a manual switch for energizing said electromagnet andfor initiating the energization of said corona electrode and said plateadvance mechanism, a lock-up relay for maintaining said electromagnet,said electrode, and said mechanism energized, and a disconnect switchfor deenergizing said lock-up to release said electromagnet, stop saidmechanism and deenergize said electrode in response to the completion oftravel of an image plate under said electrode.

6. A transfer device for the electrostatic transfer of imagescomprising, in combination, a grid of corona discharge wires, anelectrically driven plate advance conveyor mechanism to pass an imageplate and superimposed transfer sheet under said grid, 2, sheet feedchute for feeding a transfer sheet onto the face of said image plateprior to its passage under said grid, a stop for indexing said imageplate and transfer sheet with respect to each other prior to passagethereof under said grid, an electromagnet for retracting said stop fromits operative position, a manual switch for energizing saidelectromagnet and for initiating the energization of said corona gridand said plate advance mechanism, a lock-up relay for maintaining saidelectromagnet, said grid, and said motor energized, and a disconnectswitch for deenergizing said lock-up relay to release saidelectromagnet, stop said mechanism and deenergize said grid in responseto the completion of travel of an image plate under said grid.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 287,957 Osborne Nov. 6, 1883 1,077,818 Eagar Nov. 4, 19131,842,195 Pinder Jan. 19, 1932 2,058,732 Simon Oct. 27, 1936 2,095,502Johnston Oct. 12, 1937 2,324,068 Crandell July 13, 1943 2,454,168Hartwig Nov. 16, 1948 2,483,462 Huebner Oct. 4, 1949 2,486,703 BishopNov. 1, 1949 2,544,806 Ransburg Mar. 13, 1951 2,551,582 Carlson May 8,1951 2,573,881 Walkup et a1 Nov. 6, 1951 2,576,047 Schaffert Nov. 20, i2,576,882 Koole et al. Nov. 27, 1951

1. A TRANSFER DEVICE FOR TRANSFERRING AN IMAGE MATERIAL FROM AN IMAGE PLATE TO A TRANSFER SHEET, COMPRISING IN COMBINATION, A SUPPORT FOR AN IMAGE PLATE, A TRANSFER STATION, DRIVE MEANS TO ADVANCE A PLATE ON SAID SUPPORT IN A PATH PARALLEL TO THE PLATE SURFACE PAST SAID TRANSFER STATION, A SHEET FEED GUIDE MEANS DIRECTED TOWARD SAID PATH OF PLATE ADVANCED AT AN ACUTE ANGLE GREATER THAN 30 DEGREES WITH RESPECT TO THE SURFACE OF SAID PLATE POSITIONED TO FEED A TRANSFER SHEET TO THE SURFACE OF A PLATE POSITIONED ON SAID SUPPORT AT SAID ACUTE ANGLE AND TO A POSITION IN SAID PATH ADJACENT SAID TRANSFER STATION, AN ELECTRIC DISCHARGE SOURCE AT SAID TRANSFER STATION ABOVE SAID PATH OF PLATE TRAVEL FOR PRODUCING AN ELECTRIC DISCHARGE ONTO THE BACK OF A TRANSFER SHEET OVERLYING AN IMAGE PLATE ON SAID SUPPORT, WHEREBY THE LEADING EDGE OF A TRANSFER SHEET MAY BE ELECTROSTATICALLY CLAMPED TO AN IMAGE PLATE WHILE THE MAJOR PART OF THE SHEET IS STILL AT SAID ACUTE ANGLE TO SAID IMAGE PLATE AND A CURVED CHANNEL IS FORMED ACROSS THE TRANSFER SHEET TO THEREBY ELIMINATE BULGES IN THE PORTION OF THE SHEET CLAMPED AGAINST THE IMAGE PLATE, AND MEANS TO RETRACT SAID SHEET FEED GUIDE MEANS TO DROP THE TRAILING PORTION OF THE TRANSFER SHEET ONTO THE IMAGE PLATE. 